pete <email@example.com> wrote in news:515E07CA.1347 @mindspring.com:
> Tom Potter wrote: >> >> "pete" <firstname.lastname@example.org> wrote in message >> news:515C5712.email@example.com... >> > Tom Potter wrote: >> >> >> >> How would one measure a right angle >> >> without using geometry, >> >> or the 3-4-5 relationship, >> >> >> >> and how precisely can a right angle be measured? >> > >> > I place a straight edge >> > approximately perpendicular to a straight line, >> > and then I maneuver the edge to make adjacent angles >> > of equal size. >> > >> > It's very easy to accurately compare adjacent angles. >> > >> > I can't state the precission. >> > >> > -- >> > pete >> >> Okay, >> let's assume that a laser beam is a "straight line" >> over the range of interest, >> >> and let us "place a straight <laser beam> >> approximately perpendicular to <the> straight line," >> >> and juggle the "approximately perpendicular straight line" >> until the "adjacent angles" are equal, >> >> how do we compare the "adjacent angles"? > > The best that I can explain it > is just that it is very easy to see, simply by looking, > which of two adjacent supplementary angles, > if either, is bigger. > > At this link, > http://regentsprep.org/Regents/math/geometry/GP5/SuppAng.gif > you should be able to tell that angle 2, > is bigger than angle 1, > just by looking at them. > > Try it. > Get some paper, a straight edge, and a pencil. > Draw a line. > Reposition the straight, > and draw a perpendicular line. > > You shouldn't need a protractor > to be able to tell if you got it right. >
I would set the point of my compass at the point of intersection. Then draw a circle about that point. The circle intersects the line at A and B, and the perpendicular at C. Set the point of the compass at C and the pencil at A and draw another circle. If it falls short of B or over shoots B, then you'll know which angle is bigger. Or does that violate the rule of "without using geometry"?